I've heard of this before, c_b. Not sure I have this right, but I believe deafness in dogs who are in or near water may be more common than in other breeds because they're more prone to inner ear infections. If the infection isn't diagnosed/treated immediately, deafness can result. I suppose that since you don't often hear dogs complain about ear pain, an infection can easily be missed? (Or if they *are* complaining, most of us wouldn't pay attention. Silly humans.)

a.k.a. cão de agua. "For centuries, members of the breed have lived on the boats of Portuguese fishermen. They are able swimmers and can be taught to catch in their mouths and bring back fish escaping from the net. They are also useful at catching objects thrown from boats toward the shore.... but because they spend so much time in the water, they may become prematurely deaf." (Simon & Schuster's Guide to Dogs, 1980) "Huh?" (Chained_Bear, 2007)